File Extensions and How They Work

Windows 95/98/whatever-year makes working with various types of files automatic--mostly. However, because it is now so automatic most of the time, most people don't know what to do when the "automatic" isn't. That is, when Windows and/or Netscape don't automatically recognize the file type, we often assume we can't read it. Some of the instructions below for coping with various file types are easy. However, some of the instructions are more advanced (for instance, associating file types with applications) and may take a bit of work and a little bit of help before you feel comfortable with them. Don't give up. This is not rocket science (it is, unfortunately, computer science.... But that's another story...).
How File Extensions Work | Common File Extensions | Where Can I Find Out More? | Help! I'm Still Lost!

How File Extensions Work

File extensions are usually added automatically to the file name when you save a document. Many operating systems, including Windows 95 and 98, recognize common file extensions and will open the file in the correct application automatically. For example, double-clicking on a file named "this.doc" will open the document using Microsoft Word for Windows. If you have problems with opening files, check the file extension.

Sometimes you can "fix" the problem simply by renaming the file with the correct file extension. For example, if a student creates a file using Microsoft Word but sends it to you with the name: Mydocument.feb (where they have changed the file extension to the month they created the file), you can open it simply by renaming it to Mydocument.doc. However, if the file was created with another program, such as Microsoft Works for Windows, this won't work--you will need to know what type of file it is.

If you know you have the correct application, but Windows does not open the application automatically, you can do one of two things:

  1. Open the application, then use the "File" and "Open" menu commands to open the file, or
  2. Tell Windows to associate the file extension with a particular program. For example, many Windows systems are set to automatically open .htm and .html documents with Microsoft Internet Explorer. To change the system so that these files will automatically be opened in Netscape Communicator instead, you will need to

Sometimes the file extension is correct, but you do not have the correct application to read the file. (See the table below for a list of some Common File Extensions.) For instance, many students create documents using Microsoft Works (the file will have the .wps extension). Neither Microsoft Word nor Corel Word Perfect will read Works documents; you must have Works to read it.... Students using Microsoft Works should be instructed to save the file (using the "Save As" feature) in a format you can read. (For more information on using the "Save As" feature, see "Creating MLA-Style Manuscripts" for either Word Perfect or Word. The instructions for saving the document are the same for Works.)


Common File Extensions

Common File Extensions

Text Formats
 
.doc Word or WordPerfect
.latex LaTeX file
.pdf portable document file
.ps PostScript file
.rtf Rich Text Format
.tex TeX file
.txt, .text ASCII or Simple Text format
.wpd WordPerfect Document

Audio, Video, and Graphics Files
 
.au audio file
.avi movie file
.bmp Windows Bitmap graphics format
.gif graphics file
.jpg, .jpeg graphics file
.mov, .qt Apple QuickTime movie
.mpg, .mpeg audio and video formats
.ra, .ram Real Audio formats
.tif, .tiff graphics file
.wav, .wave audio file

Presentation Formats
 
.ppt PowerPoint presentation
.shw Core Presentation

Application Formats
 
.bat Batch file
.exe Executable file
.js Java Script
.pl Perl Script

Compression Formats
 
.arj File archiving
.gz, .gzip Compression format
.hqx Macintosh BinHex compression format
.lha File compression format
.zip PkZip compression format

Multimedia Formats
 
.htm, .html HyperText Markup Language 
.vrml Virtual Reality Markup Language 
.sgml Standard Generalizable Markup Language

Reprinted from writing@online.edu by Janice R. Walker and John Ruszkiewicz (New York: Longman, 1999), p. 60.  All rights reserved.

Where Can I Find Out More?

One of the best sources I know for information about almost anything related to the Internet is ZD Net's "Help and How-To. The ZDWebopedia allows you to enter a term to be defined (such as .html or "file compression") and returns links to more information than you ever wanted.

Netscape also offers information on plug-in's (programs that work from within Netscape to allow you to play audio, video, or other types of multimedia files). For instance, in order to read .pdf (portable document format) files, you must have the free Acrobot Reader plug-in. Most of these applications are free, downloadable files, and many of them should already have been installed with newer versions of Netscape. However, you may need to update the plug-in's from time to time as new versions are released. You can find out more by clicking on "Help" in Netscape and then clicking on "About Plug-ins." Netscape can also automatically recognize which plug-ins you already have installed and recommend additional plug-ins you may need.

If you already have the plug-in or application, you may simply need to tell Netscape to associate the file type with the correct plug-in or application. You can do this in Netscape by clicking on "Edit" and then choosing "Preferences" from the menu bar. Next, select "Navigator" and then "Applications." Locate the description of the file type in the scrolling box, click on "Edit," and choose the application using the "Browse" button.

Help! I'm Still Lost!

Don't feel bad! As I warned you at the beginning of this page, some of this is confusing. Luckily, help for faculty in the Department of Writing and Linguistics is only an email away (at least, as long as we continue to have funding for our Instructional Support person). Help for students (as well as faculty and staff) is also available through Computer Services Help Center.


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Copyright 2000 J. Walker